Radio frequency identification (RFID) is a technology that works on radio frequency signals. An RFID system often comprises three main components: (1) an RFID tag which stores data is usually attached to an article that one desires to identify and/or track; (2) an RFID reader that communicates with the RFID tag using radio frequency signals to obtain data from the RFID tag; and (3) a host data processor that uses the data obtained by the RFID reader from the RFID tag. If the RFID tag is within range of the radio frequency signals (radio waves), a communication link between the two RFID devices is established and the RFID tag replies with data to the RFID reader. Based on this reply, the RFID reader may identify the article.
There are various types of RFID tags. Passive RFID tags do not include a power source, such as a battery. Passive RFID tags rely on power derived from radio waves from the RFID reader to transmit a reply to the RFID reader. Active RFID tags include a power source to power its internal circuitry and to enable transmission of a reply to the RFID reader. Semi-passive RFID tags include a power supply to power its internal circuitry but relies on power derived from the radio waves from the RFID reader to transmit a reply to the RFID reader.
An important factor is range, which refers to the maximum distance between the RFID reader and RFID tag for a reliable communication link between the two RFID devices. The range is affected by various factors, such as background radio frequency noise, surrounding structures that may affect the radio waves from the RFID reader, antenna configurations of the reader and tag, relative orientation (angle) between the reader and tag, and carrier frequency. RFID systems may operate in different frequency bands. In the low frequency (LF) band, a carrier frequency of 125 kHz or 134 kHz, for example, may provide a range up to 10 cm. In the high frequency (HF) band, a carrier frequency of 13.58 MHz, for example, may provide a range up to 1 meter. In the ultra high frequency (UHF) band, a carrier frequency within 860-960 MHz, for example, may provide a range up to 15 meters.
RFID tags are used on a great variety of articles. The articles can be items of clothing for sale in a retail shop, medical devices, and individual components used in a factory, just to name a few. It is often the case that RFID tags manufactured in bulk have the same range. However, articles on which the RFID tags are attached might be stacked within a box, and the box may be surrounded by other boxes when the RFID tags must be read by an RFID reader. To ensure reliable communication, the RFID tags may be over-designed or conservatively designed to work in the most extreme situation that is expected during the useful life of the RFID tags, but such an approach may increase costs significantly. This scenario and others present a need for a system and method that allows for cost-efficient modification of an RFID tag to customize its range.